Gila Group
geological formation in New Mexico
The Gila Group is a group of geologic formations found along the upper tributaries of the Gila River in Arizona and New Mexico. Radiometric dating of lava flows within the group yields an age of Miocene to Quaternary.
Description
The group is primarily conglomerate composed of clasts (rock fragments) weathered from nearby outcrops. There are also occasional thin sandstone and tuff beds and basalt flows. Total thickness is 1,000–1,500 feet (300–460 m). Radiometric ages of basalt flows within the group range from 12.1 million years (Ma) to 1 Ma.
The group is similar in age and character to the Santa Fe Group. Both are sedimentary fill of extensional basins. The two groups are separated by the Continental Divide, and the Gila Group is separated from formations of similar age to the north by the Rim Divide, which separates the San Francisco and Salt River drainage basins to the south from the Little Colorado River drainage basin to the north.
Fossils
The Gila Group has yielded a diversity of fossils at Pearson Mesa (32.643°N 108.968°W / 32.643; -108.968).
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